The present invention relates generally to speech-to-speech translation systems and, more particularly, to methods and apparatus that perform automated speech translation.
Speech recognition techniques translate an acoustic signal into a computer- readable format. Speech recognition systems have been used for various applications, including data entry applications that allow a user to dictate desired information to a computer device, security applications that restrict access to a particular device or secure facility, and speech-to-speech translation applications, where a spoken phrase is translated from a source language into one or more target languages. In a speech-to-speech translation application, the speech recognition system translates the acoustic signal into a computer readable format, and a machine translator reproduces the spoken phrase in the desired language.
Multilingual speech-to-speech translation has typically required the participation of a human translator to translate a conversation from a source language into one or more target languages. For example, telephone service providers, such as ATandT Corporation, often provide human operators that perform language translation services. With the advances in the underlying speech recognition technology, however, automated speech-to-speech translation may now be performed without requiring a human translator. Automated multilingual speech-to-speech translation systems will provide multilingual speech recognition for interactions between individuals and computer devices. In addition, such automated multilingual speech-to-speech translation systems can also provide translation services for conversations between two individuals.
A number of systems have been proposed or suggested that attempt to perform speech-to-speech translation. For example, Alex Waibel, xe2x80x9cInteractive Translation of Conversational Speechxe2x80x9d, Computer, 29(7), 41-48 (1996), hereinafter referred to as the xe2x80x9cJanus II System,xe2x80x9d discloses a computer-aided speech translation system. The Janus II speech translation system operates on spontaneous conversational speech between humans. While the Janus II System performs effectively for a number of applications, it suffers from a number of limitations, which if overcome, could greatly expand the accuracy and efficiency of such speech-to-speech translation systems. For example, the Janus II System does not synchronize the original source language speech and the translated target language speech.
A need therefore exists for improved methods and apparatus that perform automated speech translation. A further need exists for methods and apparatus for synchronizing the original source language speech and the translated target language speech in a speech-to-speech translation system. Yet another need exists for speech-to-speech translation methods and apparatus that automatically translate the original source language speech into a number of desired target languages.
Generally, the present invention provides a multi-lingual time-synchronized translation system. Thus, the present invention is directed to a method and apparatus for providing automatic time-synchronized spoken translations of spoken phrases. The multi-lingual time-synchronized translation system includes a phrase-spotting mechanism, optionally, a language understanding mechanism, a translation mechanism, a speech output mechanism and an event measuring mechanism. The phrase-spotting mechanism identifies a spoken phrase from a restricted domain of phrases. The language understanding mechanism, if present, maps the identified phrase onto a small set of formal phrases. The translation mechanism maps the formal phrase onto a well-formed phrase in one or more target languages. The speech output mechanism produces high-quality output speech using the output of the event measuring mechanism for time synchronization.
The event-measuring mechanism measures the duration of various key events in the source phrase. For example, the speech can be normalized in duration using event duration information and presented to the user. Event duration could be, for example, the overall duration of the input phrase, the duration of the phrase with interword silences omitted, or some other relevant durational features.
In a template-based translation embodiment, the translation mechanism maps the static components of each phrase over directly to the speech output mechanism, but the variable component, such as a number or date, is converted by the translation mechanism to the target language using a variable mapping mechanism. The variable mapping mechanism may be implemented, for example, using a finite state transducer. The speech output mechanism employs a speech synthesis technique, such as phrase-splicing, to generate high quality output speech from the static phrases with embedded variables. It is noted that the phrase splicing mechanism is inherently capable of modifying durations of the output speech allowing for accurate synchronization.
In a phrase-based translation embodiment, the output of the phrase spotting mechanism is presented to a language understanding mechanism that maps the input sentence onto a relatively small number of output sentences of a variable form as in the template-based translation described above. Thereafter, translation and speech output generation may be performed in a similar manner to the template-based translation.
The present invention recognizes the quality improvements can be achieved by restricting the task domain under consideration. This considerably simplifies the recognition, translation and synthesis problems to the point where near perfect accuracy can be obtained.
A more complete understanding of the present invention, as well as further features and advantages of the present invention, will be obtained by reference to the following detailed description and drawings.